The development of an active, earth-abundant, and inexpensive catalyst for the oxygen evolution reaction (OER) is highly desirable but remains a great challenge. Here, by combining experiments and first-principles calculations, we demonstrate that MoS2 quantum dots (MSQDs) are efficient materials for the OER. We use a simple route for the synthesis of MSQDs from a single precursor in aqueous medium, avoiding the formation of unwanted carbon quantum dots (CQDs). The as-synthesized MSQDs exhibit higher OER activity with a lower Tafel slope in comparison to that for the state of the art catalyst IrO2/C. The potential cycling of the MSQDs activates the surface and improves the OER catalytic properties. Density functional theory calculations reveal that MSQD vertices are reactive and the vacancies at the edges also promote the reaction, which indicates that the small flakes with defects at the edges are efficient for the OER. The presence of CQDs affects the adsorption of reaction intermediates and dramatically suppresses the OER performance of the MSQDs. Our theoretical and experimental findings provide important insights into the synthesis process of MSQDs and their catalytic properties and suggest promising routes to tailoring the performance of the catalysts for OER applications.

Covalent organic frameworks (COFs) have attracted surging interest lately due to their wide potential in several frontline application areas like gas storage, sensing, photovoltaics, fuel cells, active catalyst supports, and so on. However, only very few reports are available for the metal-free electrocatalysis over COFs. Herein, we developed a new thiadiazole-based COF, C4-SHz COF, through the reaction between 1,3,5-tris(4-formylphenyl)benzene and 2,5-dihydrazinyl-1,3,4-thiadiazole that possesses a very high specific surface area of 1224 m 2 g −1 , unique molecular architecture, high porosity, and abundant active sites. The as-synthesized C4-SHz COF displayed superior electrocatalytic oxygen evolution reaction (OER) activity and excellent long-term durability. The electrocatalytic performance of the C4-SHz COF achieved a current density of 10 mA/cm 2 at an overpotential of 320 mV. The higher activity of the C4-SHz COF could be attributed to the high Brunauer−Emmett−Teller surface area, porosity, and network structure of the π-conjugated organic building blocks, which allowed fast charge and mass transport processes. This work validates the promising potential of a metal-free COF electrocatalyst toward the OER and its capability to replace carbon-based electrocatalysts.

The development of efficient materials for the generation and storage of renewable energy is now an urgent task for future energy demand. In this report, molybdenum disulphide hollow sphere (MoS2-HS) and its reduced graphene oxide hybrid (rGO/MoS2-S) have been synthesized and explored for energy generation and storage applications. The surface morphology, crystallinity and elemental composition of the as-synthesized materials have been thoroughly analysed. Inspired by the fascinating morphology of the MoS2-HS and rGO/MoS2-S materials, the electrochemical performance towards hydrogen evolution and supercapacitor has been demonstrated. The rGO/MoS2-S shows enhanced gravimetric capacitance values (318 ± 14 Fg−1) with higher specific energy/power outputs (44.1 ± 2.1 Whkg−1 and 159.16 ± 7.0 Wkg−1) and better cyclic performances (82 ± 0.95% even after 5000 cycles). Further, a prototype of the supercapacitor in a coin cell configuration has been fabricated and demonstrated towards powering a LED. The unique balance of exposed edge site and electrical conductivity of rGO/MoS2-S shows remarkably superior HER performances with lower onset over potential (0.16 ± 0.05 V), lower Tafel slope (75 ± 4 mVdec−1), higher exchange current density (0.072 ± 0.023 mAcm−2) and higher TOF (1.47 ± 0.085 s−1) values. The dual performance of the rGO/MoS2-S substantiates the promising application for hydrogen generation and supercapacitor application of interest.

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